The present invention relates to the processing of video signals, and particularly to software clamping of video signals.
Instruments for making measurements on video signals, such as waveform monitors, are specialized oscilloscopes which include hardware for clamping video signals. Such clamping is required when the source video signal is AC coupled because the signal's vertical level shifts as the active picture level shifts. As a result waveform monitors typically clamp either a back porch portion or a sync tip portion of the composite video signal to a specified DC voltage so that the signal's vertical level does not shift as the active picture level shifts.
However general purpose oscilloscopes do not include hardware necessary for clamping video signals. Therefore in order to use general purpose oscilloscopes for making video signal measurements, an external video display clamp is required prior to video signal input to and acquisition by the general purpose oscilloscope.
What is desired is a method of providing clamping of video signals input to a general purpose oscilloscope without the requirement of added hardware, such as an external video display clamp.